A MARX generator is a way of realizing a pulse modulating power source, and it is a device that is charged in parallel and then discharged in series using capacitance. The MARX generator can realize nanosecond narrow pulse and a very high pulse frequency. A solid-state pulse modulating power source is a power source that uses a solid-state switch, e.g. IGBT (Insulating Gate Bi-polar Transistor), to perform pulse modulation. At present, the solid-state pulse modulating power sources that are based on the MARX generator principle and are applied to linear accelerators usually work in such a way as that all of the IGBTs are triggered simultaneously.
In a power source system having a magnetron as the load, owing to the impedance characteristic of the magnetron per se, a pulse front edge slope meeting a specific requirement is necessary in order to make the magnetron operate in a specific pulse current. FIG. 1 is a schematic drawing of a pulse current waveform when the pulse front edge slope meets the requirement. FIG. 2 is a schematic drawing of a pulse current waveform when the pulse front edge is too steep, in the figure, the top of the pulse has an obvious top drop phenomenon. FIG. 3 is a schematic drawing of a pulse current waveform when the pulse front edge is too flat, in the figure, the top of the pulse has an obvious top rise phenomenon. Besides, when the amplitude of the pulse current changes, the pulse front edge slope that can maintain the top of the pulse current waveform to be even and straight will also change, and a larger amplitude requires a steeper front edge slope.
To solve the problem of uneven pulse top, the commonly adopted solution at present is to connect an inductor in series to the pulse power source output. When the amplitude of the pulse current needs to be adjusted, the inductance of the inductor can be adjusted to match the impedance. This method has a defect, which is that when the pulse current amplitude needs to be adjusted frequently, adjusting the inductance will be a very tedious procedure; especially for solid-state pulse modulating power sources used on dual-energy accelerator products, because the pulse current amplitude changes alternately in each pulse period, the method of adjusting the inductance so as to adjust the pulse current amplitude cannot be realized in these products.
Hence, there is the need for a convenient control to the output pulse front edge so as to be better adapted to the magnetron load.